Generally, it is very advantageous to know the condition or state of a vehicle when a traffic accident has occurred involving the vehicle, in order to look into the cause of the accident. As an example of apparatus representative for storing data at a traffic accident occurrence time, a flight recorder mounted on an aircraft is well known. The flight recorder for an aircraft receives and records data such as the speed, acceleration, etc. of the aircraft body through wires from hydraulic cylinders, the speed indicator, sensors, etc. in the aircraft continuously while the aircraft is flying. The recording operates at least for the time from when the airplane has once taken off until it has landed.
Such a flight recorder is a very large scale and complex apparatus which, as stated above, needs data supplied from the hydraulic cylinders, speed indicator, sensors, etc. in the aircraft; there are no known examples where such a system is mounted on vehicles other than large aircraft.
On the other hand, in a traffic accident involving a vehicle such as a ship and a car, other than an aircraft, it is also very advantageous to analyze data of, for example, acceleration, angular velocity, etc. of the vehicle at the accident occurrence time, in order to look into the cause of the accident. However, because an aircraft flight recorder is a very large scale apparatus, it is not practical to apply such a system to other vehicles because of the complex mounting requirements, costs, etc., although it is theoretically possible.
The British patent publication GB 2,020,127 A discloses an accident recording system including an accelerometer. This system merely stores acceleration data during a certain time period until the vehicle speed and acceleration become zero. Therefore, this time period may not contain a traffic accident occurrence time. Also, because the above system measures only the speed and acceleration, it is not possible to know what the orientation of the vehicle has been, i.e., whether the vehicle has turned sideways or slipped sideways in an accident.
The present invention has been made in view of the foregoing situation; it is an object of this invention to provide a traffic accident data recorder, with which it is possible to determine a traffic accident occurrence time, and obtain acceleration and/or angular velocity data during a predetermined time period after or before and after the recognized time. By obtaining the angular velocity data, it is possible to know what the orientation of the vehicle has been. It is another object of the invention to provide a traffic accident reproduction system, which can reproduce the traffic accident from the acceleration and/or angular velocity data stored in the traffic accident data recorder.